1. Field of the Invention
The present invention relates to a light source apparatus and a fabrication method thereof, and more particularly, to a light source apparatus and a fabrication method thereof capable of not only collecting light emitted from the front of a stem without losing light emitted from each light emitting device but also easily bonding a sub-mount to the stem by forming through holes on the sub-mount.
2. Description of the Background Art
A light emitting device which is currently and actively being used is typically divided into a laser diode (LD) and a light emitting diode (LED).
The LD is being widely used as a light source in the field of optical communication, and has lately been used as an important component in the field of optical media such as a DVD player, a laser disc (LD) player, a mini disc (MD) player, or the like as well as in the filed of a compact disc (CD) player and a compact disc rewritable (CD-RW) player.
In addition, the LED is widely used in a backlight unit (BLU), and is used as a light source apparatus which is located at a lower portion of an LCD PANEL which cannot emit by itself and allows an LCD to be recognized by irradiating uniform plane light.
Advantageously, the LED can be operated at a relatively low voltage, generates less heat because of high energy efficiency and has a long life span.
FIG. 1 is a longitudinal sectional view showing the conventional light emitting device, and FIG. 2 is a longitudinal sectional view showing the conventional light source apparatus.
As shown in FIG. 1, the conventional light emitting device 10 is constructed in such a manner that a buffer layer 12, an n-contact layer 13, an active layer 14 and a p-contact layer 15 are sequentially deposited over a sapphire, n-GaAs or other substrate 11 by a chemical vapor deposition (CVD) method.
A current spraying layer 16 is formed on an upper surface of the p-contact layer 15. A p-electrode 17 electrically which connects with the p-contact layer 15 and the current spraying layer 16 is formed on an upper surface of the current spraying layer 16. Next, an n-electrode 18 is formed on an upper surface of an exposed portion of the n-contact layer 13.
As shown in FIG. 2, in the conventional light source apparatus 40, the light emitting device 10 is bonded to a sub-mount 20 by a wire bonding method, and the sub-mount 20 is bonded to a stem 30. At this time, the p-electrode 17 of the light emitting device 10 connects with an electrode 21 of the sub-mount 20 by a wire 17a in order to apply an external power source, and the electrode 21 of the sub-mount 20 connects with an electrode 31 of the stem 30 by another wire 22. Since the n-electrode 18 has the same structure as the p-electrode 17, a description for a connection structure of the n-electrode 18 will be omitted hereinafter.
An operation of the conventional light source apparatus having such a construction will be described as follows.
As shown in FIGS. 1 and 2, when a voltage is applied to the electrode 31 of the stem 30, a current is applied to the p-electrode 17 and the n-electrode 18 through wires 17a and 22.
At this time, holes and electrons are injected into the p-electrode 17 and the n-electrode 18, respectively. The injected holes and electrons are introduced into the p-contact layer 15 and the n-contact layer 13 and then are recombined in the active layer 14. At this time, extra energy is changed into light, which is emitted.
However, since the conventional light source apparatus uses a light emitting device by directly attaching the light emitting device in the form of a chip to a stem, a printed circuit board, a precise wire boding procedure is required and thus the reliability is lowered.
In addition, in case of a light source apparatus in which a light emitting device is attached to a sub-mount and then the sub-mount is attached to a stem, light interference between the light emitting devices adjacent to each other occurs or light emitted from the side of the light emitting device is not collected toward the front of the stem but disperses in all directions, thereby decreasing luminous efficiency.
In addition, since a wire bonding method is used in electrically connecting the sub-mount with the stem in order to supply an external power source, a defective rate is high, process compatibility with other components is difficult because of wires, a long time is taken to process, and product reliability is deteriorated.
Moreover, since heat generated from the light emitting device is transmitted to the stem through the sub-mount, heat generation is delayed to thereby reduce a life span of the light emitting device, the work of the assembly and productivity are deteriorated.